After Nadari, an international art dealer, Vaughn became his lover and second-in-command after becoming pregnant with his child. She was put in charge of one of his casinos and Nadari had one of his drivers, Carlos Riva, work under Vaughn. Vaughn later hired Declan O'Rourke to help her manage the club without telling him who the real boss was. After being informed by former rape victim Clare Wilson that one of the people gambling in the casino, Amanda Rollins, is a police officer, she has O'Rourke and Riva bring Rollins to the back of the casino, where they rip off her shirt. When they realize she isn't, they blackmail her. Later, when Rollins tells them she is unable to make the parking tickets go away, Vaughn tells her to get the address of a woman who is on the jury for an insurance fraud case.

When a Brazilian ambassador named Marcelo Guarani comes to gamble in the casino, she tells him that Nadari is getting impatient and then tells Wilson to not give him any more drinks. When she goes into the back room of the casino after Rollins and O'Rourke had sex, she tells him to leave and watch the floor. She and Rollins then speak with each other. Later, when O'Rourke and Vaughn asks Rollins to drive Guarani home, she tells them that their waitress, Wilson, is only a sixteen-year-old girl, much to her shock. As Rollins leaves, Vaughn has O'Rourke fire Wilson. When Riva gets caught with an unregistered gun, Vaughn sends him and O'Rourke to get Rollins to get the gun and bring it to them so the charge against Riva would go away. When Rollins brings Vaughn the gun, she tells Rollins that it helped her pay her debt. After the Brazilian embassy home invasion, Rollins goes to Vaughn and tells her that Riva's DNA was in the system. She reveals that Riva lied when he told Rollins the DNA wasn't in the system. When Rollins asks why she ordered Marcelo Guarani's wife Marianna to be raped, Vaughn tells her that she did so to send a message. Vaughn then tells Rollins to figure out a way to keep Riva from being charged for rape.

When Rollins tells Vaughn that she is going to go to jail for being an accessory to rape, Vaughn tells her that if she tries to cut a deal, she will have her killed for it. She then tells Rollins about how a police officer that tried to cut a deal against them was killed for it and that his death was staged to look like a suicide. Rollins then pulls out a gun and holds it to Vaughn's belly, in order to force her to take Rollins and O'Rourke to Nadari. When they get there, Rollins demands money and transportation out of the country when the police realize her involvement, and Nadari agrees to help her. O'Rourke later takes advantage of Vaughn having contractions to take Rollins' gun, and Nadari orders him to shoot her. O'Rourke then reveals his status as an undercover officer and arrests everyone there, save Rollins. Vaughn later turns in evidence to help the police charge Nadari for multiple counts of money laundering, illegal gambling, art forgery, rape, and murder. (SVU: "Gambler's Fallacy")